Machine having electrical power system and centered drive coupling for same

Abstract

A machine, such as an electrically powered track type tractor, includes an engine configured to rotate a generator. A drive coupling has a first element fixed to rotate with the engine and a second element fixed to rotate with the generator. The first and second elements are configured to rotationally couple together for transmitting torque from the engine to the generator, but configured to allow relative slip between the first and second elements. The relative slip may occur during engine start up as rotational rates pass through a range associated with the excitation of resonance torsional vibrations. A centering ring has a radial outer surface in contact with the first element and a radial inner surface in contact with the second element. The centering ring assists in avoiding an off center drive coupling arrangement while electrically isolating the first element from the second element.

1. An electrical power system for a machine comprising:
 a generator configured to generate electrical power for the machine; 
 an engine configured to rotate the generator; 
 a drive coupling having a first element fixed to rotate with the engine and a second element fixed to rotate with the generator, the first and second elements being configured to rotationally couple together for transmitting torque from the engine to the generator, the drive coupling being further configured to allow relative slip between the first and second elements; and 
 a centering ring with one of a radial outer surface and a radial inner surface in contact with the first element and an other of the radial outer surface and the radial inner surface in contact with the second element, and the centering ring electrically insulating the first element from the second element. 
 
     
     
       2. The system of  claim 1  wherein the radial outer surface of the centering ring is in contact with the first element; and
 the radial inner surface of the centering ring is in contact with the second element. 
 
     
     
       3. The system of  claim 2  wherein the centering ring is received in a radial groove defined by a coupling rim of the second element. 
     
     
       4. The system of  claim 3  wherein the radial groove has a depth less than a radial thickness of the centering ring. 
     
     
       5. The system of  claim 4  wherein the centering ring has a rectangular cross section. 
     
     
       6. The system of  claim 1  wherein the centering ring is rotatable about a central axis with respect to the first element and the second element. 
     
     
       7. The system of  claim 1  wherein the centering ring is comprised of polytetrafluoroethylene. 
     
     
       8. The system of  claim 7  wherein the outer radial surface of the centering ring is in contact with the first element;
 the radial inner surface of the centering ring is in contact with the second element; 
 the centering ring is received in a radial groove defined by a coupling rim of the second element; 
 the radial groove has a depth less than a radial thickness of the centering ring; and 
 the centering ring is comprised of polytetrafluoroethylene and with a rectangular cross section. 
 
     
     
       9. A machine comprising:
 a frame; 
 an engine mounted to the frame; 
 a generator configured to generate electrical power for the machine and coupled with the engine; 
 a drive coupling configured to transmit torque between the engine and the generator, the drive coupling being further configured to allow relative rotation between the engine and the generator; 
 the drive coupling including a centering ring with one of a radial outer surface and a radial inner surface in contact with a first element fixed to rotate with the engine and an other of the radial outer surface and the radial inner surface in contact with a second element fixed to rotate with the generator, and the centering ring electrically insulating the first element from the second element. 
 
     
     
       10. The machine of  claim 9  comprising a propulsion system for the machine which includes the generator, the engine and the drive coupling, and electrically powered ground engaging elements coupled with the generator which are configured to propel the machine. 
     
     
       11. The machine of  claim 10  wherein the engine includes flywheel;
 the generator includes an input shaft; and 
 the flywheel, the input shaft and the centering ring are coaxial. 
 
     
     
       12. The machine of  claim 11  wherein the radial outer surface of the centering ring is in contact with the first element; and
 the radial inner surface of the centering ring is in contact with the second element. 
 
     
     
       13. The machine of  claim 12  wherein the centering ring is received in a radial groove defined by a coupling rim of the second element;
 the radial groove has a depth less than a radial thickness of the centering ring; and 
 the centering ring has a rectangular cross section. 
 
     
     
       14. The machine of  claim 13  comprising an electric drive track-type tractor having a first track and a second track comprising the ground engaging elements, wherein the drive coupling further comprises a spring coupling configured to allow oscillatory torsional compliance between the output shaft and the input shaft and a friction disc configured to transfer torque between the output shaft and the input shaft, the friction disc further being fixed to rotate with one of the input shaft and the output shaft and configured to slip relative to the other of the input shaft and the output shaft to allow the non-oscillatory relative rotation. 
     
     
       15. A method of rotationally coupling an engine to a generator comprising the steps of:
 mounting a centering ring on a coupling rim of a second element of a drive coupling; 
 maneuvering the coupling rim into a central opening of a piston of a first element; 
 centering the coupling rim in the piston by contacting an outer radial surface of the centering ring with a radial inner surface of the piston; 
 electrically isolating the first element from the second element; 
 fixing the first element to rotate with the engine; and 
 fixing the second element to rate with the generator. 
 
     
     
       16. The method of  claim 15  wherein the step of fixing the first element to rotate with the engine includes clamping a friction disk of the second element between the piston and a reaction plate of the first element. 
     
     
       17. The method of  claim 16  wherein the clamping step includes bolting the reaction plate to a flywheel of the engine. 
     
     
       18. The method of  claim 17  wherein the centering step includes sliding the centering ring on the radial inner surface of the piston. 
     
     
       19. The method of  claim 18  including a step of setting a clamping load on the friction disc by compressing a biaser between the piston and the flywheel during the clamping step. 
     
     
       20. The method of  claim 19  wherein the step of fixing the second element to rotate with the generator includes spline mating a generator input shaft to a hub adapter of the second element.